function lavaFunc(){
  window.lavaVar += 90;
  document.getElementsByClassName("lavaLamp")[0].style.filter = "hue-rotate("+window.lavaVar+"deg)";
  document.getElementsByClassName("lavaLamp")[0].style.animationName = "none";
  setTimeout(function(){
    document.getElementsByClassName("lavaLamp")[0].style.animationName = "";
    document.getElementsByClassName("lavaLamp")[0].style.animationPlayState = "running";
  }, 50);
}
window.lavaVar = 0;